SUBSTITUENT EFFECTS ON THE ³¹P, ¹³C, AND ¹H NMR CHEMICAL SHIFTS OF SUBSTITUTED DIPHENYL 1-PHENYLAMINO-1-PHENYLMETHANEPHOSPHONATES AND THEIR ANIONS

Abstract

For a series of thirty-five novel diphenyl 1-phenylamino-1-phenylmethanephosphonates, substituted in the meta and para positions on the anilino and/or aryl ring, ³¹P chemical shifts show a good linear correlation with Hammett σ_n and Taft σ° parameters, the ³¹P nucleus being better shielded in the case of electron withdrawing substituents. The same pattern is observed for the phosphonate anions, except when para phenyl substituents can interact with the phosphorus atom by direct resonance. This inverse relationship is due to a field effect of the substituent dipole which polarizes π-electron clouds in the molecule. A corresponding shift in π-electron density is likewise observed for ¹³C resonances of the two diastereotopic phenoxy groups, the phenylamino and phenyl moieties. Vicinal CH-NH coupling is shown to be dependent on the rate of NH proton exchange as influenced by resonance, temperature and solvent effects.